The relationship Between Earliness and Vigour in Wheat (Triticum aestivum L.)

Felicity Harris

    Research output: ThesisDoctoral Thesis

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    Abstract

    Wheat (Triticum aestivum L.) is the most widespread winter crop sown in
    south-eastern Australia, where it is often grown under water-limited
    conditions. Grain yield potential is increased when cultivars have phasic
    development adapted to the environment in which they are grown, and are
    capable of accumulating biomass whilst maintaining water-use efficiency to
    achieve a high harvest index. There has been some anecdotal evidence that
    suggests rate of development and the accumulation of biomass may be
    associated, with reports that early-maturing cultivars grow faster than latermaturing cultivars. A series of field and pot experiments were conducted
    during 2008-11 to investigate the association between rate of phasic
    development and plant growth in wheat in southern New South Wales. The
    experiments presented in this thesis show that later maturing, vernalisationresponsive genotypes accumulate biomass slower than early-maturing genotypes. Photoperiod and vernalisation genes have a significant influence on developmental rate. These genes are described as regulatory genes and have been shown to influence plant traits in addition to their effect on
    phenology. The influence of these genes on early growth in wheat is
    unknown, though information pertaining to these effects would make a
    significant contribution to breeder’s ability to ‘design’ genotypes suited to
    various environments and farming systems. The investigations undertaken
    were divided into two main areas: (i) the physiological association between
    rate of plant development and early growth; and (ii) the role of vernalisation
    and photoperiod genes in regulating plant development and growth.

    A positive correlation between shoot and root biomass was established for a
    group of cultivars, indicating that differences in growth rate were not due to
    genotypic variation in the distribution of biomass. Using lines from a
    doubled-haploid population from the cross Janz/Diamondbird, the effect of
    Ppd-B1, Ppd-D1, Vrn-A1, Vrn-B1 and Vrn-D1 on anthesis date, plant stature
    and growth were measured. The effect of these genes was to account for
    75% of the genotypic variance in anthesis date and 85% of the genotypic
    variance in plant stature in the given population. Presence of the winter
    allele at either Vrn-A1 or Vrn-B1 delayed anthesis and reduced plant stature.
    Genotypes with winter alleles at all three VRN1 loci (Vrn-A1v + Vrn-B1v +
    Vrn-D1v), classified as winter types, had the largest delay in anthesis date
    and the lowest plant stature scores. Presence of the winter allele Vrn-B1v
    consistently reduced biomass and slowed crop growth rate compared with
    the spring allele Vrn-B1a. In one experiment Vrn-A1v suppressed growth
    relative to Vrn-A1a. It is suggested that the effect of VRN1 genes on plant
    growth is a pleiotropic effect of these genes. The effect of VRN1 genes on
    plant growth is not consistent with their effect on development and plant
    stature. Whilst anthesis date was further delayed and plant stature reduced
    by sequential substitution of spring alleles with winter alleles, the
    suppression of growth reported for Vrn-B1v (and Vrn-A1v) was not
    enhanced by the presence of winter alleles at the other VRN1 loci. These
    differences in growth rate are not evident in controlled glasshouse
    experiments characterized by relatively high growing temperatures or in a
    field experiment where sowing was significantly delayed and temperatures
    were not cold enough to saturate the vernalisation response of winter
    genotypes.

    This study has attributed the association observed between vigour and
    earliness in wheat to a pleiotropic effect of the VRN1 genes rather than a
    direct association with development per se. These genes delay anthesis and
    reduce plant stature in vernalisation-responsive genotypes, and when
    expressed under cold temperatures, they are capable of suppressing plant
    growth
    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    • Charles Sturt University
    Supervisors/Advisors
    • Virgona, James, Co-Supervisor
    • Angus, John, Co-Supervisor
    • Martin, Peter, Co-Supervisor
    • Condon, Jason, Co-Supervisor
    Award date01 Aug 2015
    Place of PublicationAustralia
    Publisher
    Publication statusPublished - 2016

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